Cement plug



Sem., s, m2?, www@ H. A. DAVIS ET AL CEMENT PLUG Filed April 22, 1924 lPatented Sept. 6, 1927.

UNITED stares alf-ENT orrica.

CEMENT PLUG.

Application led April 22, 1924. lSerial No. 708,130.

Our invention relates to cement plugs used in oil wells for closing thebottom of a well casing to be cemented after the cement has been dumpedthrough the casing into the bottom of the hole so that when the casingis lowered into the liquid cement the plug will not allow any cement tore-enter the casing, but will force the cement up on the outside of thecasing so that when it subsequently sets water cannot flow into theopening.

It is a purpose of ourfinvention to provide a cement plug of the abovedescribed character which can be inserted into a well casing to apredetermined depth, where `it seals the casing topositively prevent thepassage of cement above the plug, and automatically locks itselfagainstupward movement within the casing irrespective of the fluidpressure exerted' upwardly on the plug.

' We will describe only one form of cement plug embodying our invention,and will then point out the novel features thereof 1n claims.

In the accompanying drawings Figure l is a view showing in sideelevation and partly in section one form of cement plug embodying ourinvention in a non-sealing position within a well casing;

Figure 2 -is a view s'milar to Figure 1, showing the plug in sealingposition;

Figure 3 is a fragmentary view showing in side elevation the lowerportion of the core of the plugl shown -in the preceding :i5 views, andtaken at right angles thereto.

Referring specifically to the drawings, in which' similar referencecharacters refer to similar parts, our invention in its presentembodiment comprses a core body 15 formed of suitable material, such aswood or the like, and havingr a lower portion 16 of reduced diameter toprovide at the junction of the two a'valve 17 upon which is tted agasket 18. The reduced portion 16 of the bore body is provided withrecesses or -pockets 19 at diametrcally opposedpoints in which aremounted slips or dogs 20. A'

clevis 21 extends between the pockets and provides a pivotal mountingfor the slips 20 '50 so that under the act-ion of springs 22 the dogsare urged outwardlyfto the position shown in Figure 2. The pockets 19are such as to allow the dogs 20 to move within the area defined by thereduced portion 16 or to the position shoWn in Figure 1.

ln the present instance we have shown two well casing sections 23and 24connected by a conventional collar 25 threadedly-engaging theconfronting ends of the sections and disposed exteriorly'. thereof. Theplug includes a seat element for the valve 17, which comprises anannular member 26l1aving an exterior annular projection 27 which, inapplied position within the Well casing, is interposed between theconfronting cnds of the sections 23 and 24 and thus sustained in iixedposition Within the casing. The upper edge of the member 26 is beveled,as indicated at 28, so as to con-i form to the shape of the valve 17 andthus provide a tight seat for the latter whenused in conjunction withthe compressible gas lret 18.

1n practice, the bore body 15` and 16 is forced down into the wellcasing, and through the medium of a cable 29 connected to an eye 30secured to the upper end of the portion 15, the depth to which the plugis lowered can be definitely determined. As

the core body'moves downwardly within the i casing, the slips or dogs-20are pressed inwa-rdly against the action of the springs 22 by virtue ofthe fact that they contact with the wallsof the well casing. lt willthus be seen that they do not interfere with the lowering of theplugwithin the casing nor the extension of the portion 16 through theseat members 26. When the extenson .16 has been projected through theseat member 26 as shown'in Figure 2,v the valve 17 reposes upon the seat28, with the gasket 18 interposed between the two to provide afluidtight joint. As the valve engages the seat, the'slips or dogs 20'having movedI free of the lower end of the seat member 26, now

respond to the action of the springs 22` and move outwardly to pointsbeneath the lowerl l edge of the seatfmember, thereby locking the valveupon the seat and preventlng move-A ment of the'body upwardly within thecas`- mg.

From the foregoing operation it' will 'be manifest that the cement plugcan be lowered into a well casing rand 'automatically locked in sealingposition so as to prevent the passage ofliquid upwardly past the plug,or Vdisplacement of the plug vertically irrespective of the liquidpressure beneath the plug. In this manner the cement plug func. tions toprevent the liquid cement from re- \spirit of the invention and thespirit and scope of the appended claims.

. lVhat we claim is:

1. In combination, a well casing, a plug insertable wholly into thecasing and provided with a valve, and means having a valve seat andsecured at a predetermined point in the. easing coacting with means onthel lplug to lock the plug against movementJ vertically within theeasing when the plug has been lowered to the predetermined point lwithinthe casing to engage said valve with said' seat.

2. In combination, a well casing, a plug insertable wholly into thecasing, means adapted to be secured within the casing, and means on theplug coacting with the first means to provide a liquid tight sealbetween the plug and casing and to lock the plug lto the first means.

3. A cement plug comprising a core having a valve thereon, a memberadapted to be secured within a well casing and providing @a seat forsaid valve, and means on the core automatically engageable with saidmember to lock the core in aposition in which the valve is tightlyfitted on said seat.

4. A cement plug comprising a core having a valve thereon, a memberadapted to be secured within a well casing and provid ing a seat forsaid valve, and slips on the 4core automatically engageable with -saidmember to lock the core in a position in which the valve is tightly ttedon said seat.

5. A cement plug having a core rovided with a main portion and a reduceportion to form a valve at the junction of the two portions, a memberadapted to be secured within a well casing and providing a seat for thevalve and slips mounted in the reduced portion and urged outwardly toengage the member and lock the valveV on the seat.

6. In combination, a well easing, a-plug insertable Wholly into thecasing and having a valve, an annular member insertable'into theconfronting ends of adjacent sections of the casing and formed with avalve seat with which the valve of the plug is adapted to havefluid-tight engagement, a fixed projection on the member adapted to beeny.

gaged by and clamped between the confronting ends of the casing sectionswhen the latter-are coupled together so as to secure the j member infixed position at a predetermined point in the casing, and means on. theplug coacting with the member to lock the plug against movementvertically when the plug has been lowered into the casing with its'valve in engagement with saidA seat.

7. In combination, a well casing, a plug -insertable wholly into thecasing and having cou led together so as to secure the member l in Xedposition at a predeterminedpoint in the casing. and means on the plugcoacting with the member to lock the plug against movement verticallywhen the plug has been lowered into the casing with its valve inengagement Withlsaid seat.

8. A cement plug comprising a core including a main portion and areducedporf tion, a valve on the,core at the junction of the main and reducedportions, a member having means thereon adapted to be gripped betweenthe ends of casing sections for securing the member in fixed positionwithin a casing, a valve seat on the member upon which the valve seatswhen the reduced portion is extended through the member, and slipsmounted in the reduced portion and adapted to engage the member forlocking the valve on said seat.

9. A cement plug comprising a core including a main portion and areduced portion, a valve on the core at the junction of the main andreduced portions, an annular member having a projection on its outersurface adapted to be gripped between the ends of the casing sectionsfor securing the member in fixed position within a casing, a valve seaton the up er edge of the member upon which said va ve seats when thereduced portion is extended through the member, and spring pressed slipson the reduced portion movable to allow the passage of the reducedportion through the member, but en' gagingthe lower edge of the memberto lock the valve in tightly seated position on said seat and reventupward movement of the 'core Wit in a casing.

HERBERT A. DAVIS. CLEO F. DAVIS.

